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Urinary tract infection

A urinary tract infection is an infection that begins in your urinary system. Your urinary system is composed of the kidneys, ureters, bladder and urethra. Any part of your urinary system can become infected, but most infections involve the lower urinary tract — the bladder and the urethra.

What is it?

A urinary tract infection is an infection that begins in your urinary system. Your urinary system is composed of the kidneys, ureters, bladder and urethra. Any part of your urinary system can become infected, but most infections involve the lower urinary tract — the bladder and the urethra.

Women are at greater risk of developing a urinary tract infection than are men. A urinary tract infection limited to your bladder can be painful and annoying. However, serious consequences can occur if a urinary tract infection spreads to your kidneys.

Antibiotics are the typical treatment for a urinary tract infection. But you can take steps to reduce your chance of getting a urinary tract infection in the first place.

Symptoms

Urinary tract infections don't always cause signs and symptoms, but when they do they can include:

A strong, persistent urge to urinate

A burning sensation when urinating

Passing frequent, small amounts of urine

Urine that appears cloudy

Urine that appears bright pink or cola colored — a sign of blood in the urine

Strong-smelling urine

Pelvic pain, in women

Rectal pain, in men

Causes

The urinary system is composed of the kidneys, ureters, bladder and urethra. All play a role in removing waste from your body. Urinary tract infections typically occur when bacteria enter the urinary tract through the urethra and begin to multiply in the bladder. Although the urinary system is designed to keep out such microscopic invaders, the defenses sometimes fail. When that happens, bacteria may take hold and grow into a full-blown infection in the urinary tract.

The most common urinary tract infections occur mainly in women and affect the bladder and urethra.

Infection of the bladder (cystitis) is usually caused by Escherichia coli (E. coli), a species of bacteria commonly found in the gastrointestinal tract. Sexual intercourse may lead to cystitis, but you don't have to be sexually active to develop it. All women are susceptible to cystitis because of their anatomy — specifically, the close proximity of the urethra to the anus and the short distance from the urethral opening to the bladder.

Infection of the urethra (urethritis) can occur when gastrointestinal bacteria spread from the anus to the urethra. In addition, because of the female urethra's proximity to the vagina, sexually transmitted diseases (STDs), such as herpes, gonorrhea and chlamydia, also are possible causes of urethritis.

Risk factors

Some people appear to be more likely than are others to develop urinary tract infections. Risk factors include:

Being female. Urinary tract infections are very common in women, and many women will experience more than one. A key reason is their anatomy. Women have a shorter urethra, which cuts down on the distance bacteria must travel to reach the bladder.

Being sexually active. Women who are sexually active tend to have more urinary tract infections than women who aren't sexually active.

Using certain types of birth control. Women who use diaphragms for birth control also may be at higher risk, as may women who use spermicidal agents.

Undergoing menopause. After menopause, urinary tract infections may become more common because the lack of estrogen causes changes in the urinary tract that make it more vulnerable to infection.

Having urinary tract abnormalities. Babies born with urinary tract abnormalities that don't allow urine to leave the body or cause urine to back up in the urethra have an increased risk of urinary tract infections.

Having blockages in the urinary tract. Kidney stones or an enlarged prostate can trap urine in the bladder and increase the risk of urinary tract infection.

Having a suppressed immune system. Diabetes and other diseases that impair the immune system — the body's defense against germs — can increase the risk of urinary tract infections.

Using a catheter to urinate. People who can't urinate on their own and use a tube (catheter) to urinate have an increased risk of urinary tract infections. This may include people who are hospitalized, people with neurological problems that make it difficult to control their ability to urinate and people who are paralyzed.

Complications

When treated promptly and properly, urinary tract infections rarely lead to complications. But left untreated, a urinary tract infection can become something more serious than merely a set of uncomfortable symptoms.

Untreated urinary tract infections can lead to acute or chronic kidney infections (pyelonephritis), which could permanently damage your kidneys. Urinary tract infections may be overlooked or mistaken for other conditions in older adults. Young children also have an increased risk of kidney infections. Pregnant women who have urinary tract infections may have an increased risk of delivering low birth weight or premature infants.

Women who experience three or more urinary tract infections are likely to continue experiencing them.

Diagnosis

Tests and procedures used to diagnose urinary tract infections include:

Analyzing a urine sample. Your doctor may ask you to turn in a urine sample that will be analyzed in a laboratory to determine if pus, red blood cells or bacteria are present. To avoid potential contamination of the sample, you may be instructed to first wipe your genital area with an antiseptic pad and to collect the urine midstream.

Growing urinary tract bacteria in a lab. Laboratory analysis of the urine is sometimes followed by a urine culture — a test that uses your urine sample to grow bacteria in a lab. This test tells your doctor what bacteria are causing your infection and which medications will be most effective.

Creating images of your urinary tract. If your doctor suspects that an abnormality in your urinary tract is causing frequent infections, you may undergo tests to create images of your urinary tract using ultrasound or computerized tomography (CT). Another test called an intravenous urinary pyelogram uses X-rays to create images. During this test, a dye is injected into a vein in your arm and X-rays are taken of your urinary tract. The dye highlights your bladder and urethra and allows your doctor to determine if you have any abnormalities that slow urine from leaving your body.

Using a scope to see inside your bladder. If you have recurrent urinary tract infections, your doctor may use a long, thin tube with a lens (cystoscope) to see inside your urethra and bladder. The cystoscope is inserted in your urethra and passed through to your bladder. This procedure is called cystoscopy.